He was probably the best actual actor of the entire classic series. I still prefer Tom as the Doctor (I can't help it) but, like Michael Caine, Tom is someone who mostly plays himself. Patrick Troughton was a genuine character actor.

I remember reading somewhere that the show's producer really worked hard at getting Troughton to take the role. The reasons were that no one know if viewers would accept a change of lead actors, so the production team wanted someone of Troughton's stature and popularity, and it was hoped that having him in the role of the Doctor would make it easier to get other top level actors to appear on the program.

Yes. A lot of people nowadays seem to forget, or don't realise, that Troughton was actually a fairly well known and respected actor, back then. He was known before Doctor Who eclipsed everything else he'd ever done.